/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.facebook.presto.util;

import com.facebook.presto.spi.PrestoException;

import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import static com.facebook.presto.spi.StandardErrorCode.NOT_SUPPORTED;

public final class SecureRandomGeneration
{
    private SecureRandomGeneration() {}

    public static String getNonBlockingAlgorithmName()
    {
        String os = System.getProperty("os.name");
        return os.startsWith("Windows") ? "SHA1PRNG" : "NativePRNGNonBlocking";
    }

    /**
     * Return a non-blocking instance of SecureRandom, or throw PrestoException if not supported
     * <p>
     * With the exception of Windows machines, this uses the NativePRNGNonBlocking algorithm.
     * On Windows, this uses SHA1PRNG.
     */
    public static SecureRandom getNonBlocking()
    {
        String algorithm = getNonBlockingAlgorithmName();
        try {
            return SecureRandom.getInstance(algorithm);
        }
        catch (NoSuchAlgorithmException e) {
            throw new PrestoException(NOT_SUPPORTED, algorithm + " is not supported in your OS", e);
        }
    }
}
